This proposal is based on the premises that potent vasoactive compounds may be synthesized and released by the lung, and that the release of these substances may mediate abnormal pulmonary vascular responses such as vasoconstriction and pulmonary edema. The chemical agents on which we will concentrate are: the recently identified vasoactive lung peptides, the vasoactive intestinal peptide, and the prostaglandins and related lipids. The experimental or disease conditions in which we will assess the role of these compounds as mediators are: pulmonary edema, anaphylaxis, pulmonary embolism, acid aspiration and "shock lung".